It is important to be able to monitor the vacuum level in any sealed package such as a hermetically sealed package. This is especially true when MEMS (micro-electro-mechanical structures) devices are present in the sealed package. Various other micro-mechanical motion devices such as resonators, gyroscopes or other devices may also be operated in sealed packages. The MEMS or other devices may be part of an integrated circuit or other semiconductor device, and are designed to operate in a vacuum. If a desirably low vacuum level is not present, the MEMS device and thus the integrated circuit or other semiconductor device will malfunction. All seals cannot be perfect and the vacuum level or other desired internal pressure level can become degraded due to leaks. This is particularly true in semiconductor devices which are manufactured to include smaller feature sizes and smaller tolerances. It is extremely critical for MEMS devices of such semiconductor devices to operate at vacuum levels or at the pressure level desired. In semiconductor devices, the MEMS device may be formed over a substrate surface and a cover is joined to the substrate surface to form a hermetic seal resulting in an enclosure that includes the MEMS device.
It is difficult to measure the differential pressure between the outside air and the vacuum level in the package, i.e. in the enclosure. Sensors that are external to the enclosure cannot accurately measure the pressure, i.e. vacuum level, in the enclosure.